The preparation of diarylethylenes by the dehydrogenation of 1,1-diarylethane has been reported in U.S. Pat. Nos. 2,450,334 and 3,071,,360. U.S. Pat. No. 2,450,334 specifically describes the dehydrogenation of 1,1-di-p-tolylethane to 1,1-di-p-tolylethylene in the presence of steam and in the presence of a catalyst containing metals having atomic numbers of from 23 to 29, and their mixtures. U.S. Pat. No. 3,071,630 describes the dehydrogenation in the absence of oxygen of 1,1-diphenylethane to 1,1-diphenylethylene and to 1,2-diphenylethylene (stilbene) in the presence of a chromium-alumina catalyst. However, the process of the present invention comprising the oxydehydrogenation of the 1,1-diaryl-or the symmetrical 1,2-diarylethanes to the corresponding diarylethylenes in the presence of a metal phosphate catalyst, wherein greatly improved yields and and selectivities to the desired products can be realized, has heretofore not been described.
The diarylethylenes are of particular interest for use in the preparation of, among others, dyes and pharmaceuticals, and as monomers in the formation of novel polymeric compositions. Thus an economically feasible process for the manufacture of these starting materials is in demand.